National 4

The section of the electromagnetic spectrum with wavelengths ranging from 10nm to 400nm is called ultraviolet radiation (uv for short). Sunlight contains uv rays and it’s those uv rays that are responsible for the suntan you get during the summer holidays. This Australian animation shows how the ultraviolet in sunlight causes our skin to tan and explains why too much uv will damage our skin. The SunSmart page has loads of information on staying safe in the sun.

The damage that uv can do to cells is put to good use in some sterilisation equipment, such as this bottle for safe drinking water and the toothbrush sanitiser shown below.

The Nobel Prize for Medicine was awarded to Niels Rydberg Finsen in 1903 for his research into the effects of ultraviolet on the bacteria that cause tuberculosis.

We used uv banknote checkers in class to view some of the security features built into British banknotes. This image of a Clydesdale Bank £10 note shows part of the pattern that can only be seen under uv light.

Remember that whenever something glows under a uv light, we’re not seeing the uv radiation itself because our eyes can’t detect ultraviolet. Instead, we see the fluoresence; visible light given out in response to the uv falling on the material.

Some hair gels fluoresce under uv light. Here is someone with some of the uv gel in his hair.